1. Field
The invention is in the field of automatic sorting of items, with removal of those items which do not conform to predetermined standards, and is specifically concerned with the automatic sorting of items of agricultural produce, such as fruits and vegetables, particularly potatoes, to remove abnormal, e.g. defective items.
2. State of the Art
There are numerous machines described in the patent literature for sorting items such as fruit and vegetables. Many of these machines use light sources to illuminate the items to be sorted. In some cases the translucence of an item is a measure of its condition, defective items exhibiting different translucence than sound items. In such cases, light sensors are arranged to detect the light transmitted by the items being sorted. In other cases, the color of an item indicates its condition. In these other cases, reflected light of a certain wavelength is detected by light sensors, and associated filters pass only reflected light of that wavelength to the sensors.
Some items, such as potatoes, exhibit substantially uniform light reflectivity when in normal condition. Defects in the item exhibit different light reflectivities. In such a case, neither translucence nor wavelength of reflected light need be measured, but merely the amount of light reflected. Several sorting machines have been developed on this basis. Machines of this type usually provide several light sensors arranged to monitor respective surfaces of an item to be sorted, each such sensor being adapted to sense light reflected over an entire cross-sectional slice of the illuminated inspection area. Such machines, while satisfactory for small items like rice or beans, lose accuracy and sensitivity when used with larger items like potatoes. Moreover, no provision can be made in these machines for sorting items into different categories based upon relative size or number of defects. For example, because of the size or number of defects, a potato may be unsuitable for a particular use, but it may be economical to remove the defective portion or portions from such a potato or the potato may be suitable for another use provided the defective portion or portions do not exceed a given percentage of the total potato. Under such circumstances, it may be desirable to reject certain potatoes from the main stream and to sort the rejects into separate groups as they are rejected.